1. Field of the Invention
The present invention relates to circuit breakers, and more particularly relates to miniature type circuit breakers including a bypass feature for directing relatively high and damaging transient currents away from sensitive components in the circuit breaker to resist damage to those components.
2. Background Information
Circuit breakers of the type having an operating mechanism and trip means, such as a thermal trip assembly and/or magnetic trip assembly, which are automatically releasable to effect tripping operations and manually resettable following tripping operations are common and generally well known in the art. Examples of such circuit breakers are disclosed in U.S. Pat. Nos. 3,849,747, 4,933,653 and 5,008,645. Such circuit breakers, commonly referred to as xe2x80x9cminiaturexe2x80x9d circuit breakers, have been in use for many years and their design has been refined to provide an effective, reliable circuit breaker which can be easily and economically manufactured on a large scale. In addition, circuit breakers of this type are utilized in conjunction with ground fault mechanisms as well.
In operation, the bimetallic and other electrically sensitive components of the circuit breaker can be subjected to relatively high transient currents, such as when the circuit breaker is tripped to interrupt current through the circuit breaker. These high transient currents can be phase currents on the order of 9 kA or higher. In a relatively short period of time, then, these high transient currents can damage the components encased within the circuit breaker. This damage can reduce the useful life of the circuit breaker and/or adversely affect the proper functioning of the circuit breaker once the high transient event has occurred.
What is needed, therefore, is an apparatus for use in conjunction with a circuit breaker that can provide a bypass of the normal circuit path, especially for relatively high, potentially damaging transient currents. Such an apparatus is needed to resist damage to the sensitive components of the circuit breaker and thereby improve the reliability of the breaker, its useful life, and the general safe condition of the circuit breaker during its operation to interrupt current flow.
The present invention has met the above-mentioned needs by providing an apparatus for use in conjunction with a circuit breaker that permits at least a portion of a high transient current to bypass the normal current path through the circuit breaker.
The apparatus of the present invention provides a bypass conductor for use in a circuit breaker including first and second ends and a middle portion positioned in the circuit breaker housing. The first end is structured to be adjacent to a contact arm of the circuit breaker in an open circuit position of the circuit breaker to receive current flow, especially during a high transient current event. The second end of the bypass conductor is electrically coupled and mechanically connected to a load terminal in the circuit breaker to provide a path for a transient current between the first and second ends. The bypass conductor is preferably made of a metal such as copper or another suitable metal alloy or electrically conductive composite. In the invention, the bypass conductor provides an electrical path with a resistance that is reduced relative to the normal current path through the circuit breaker.
The apparatus of the present invention can further include an insulator such as glass tape, for example, positioned and applied to resist conductivity between electrically conductive elements in the circuit breaker and the bypass conductor of the present invention. The middle portion of the bypass conductor is preferably form-fitted around an insulated base portion of the circuit breaker.
A method for bypassing the sensitive bimetallic components in a circuit breaker is also provided by the present invention. The method includes providing a bypass conductor including first and second ends and a middle portion. The method also includes positioning the bypass conductor within the circuit breaker so that its first end is adjacent to the contact arm in an open position of the circuit breaker. Then, during a high transient current event, the method includes directing at least a portion of high transient current to the bypass conductor.
It is an object of the present invention to provide an alternative path for current flow through a circuit breaker.
It is a further object of the present invention to resist damage to bimetallic components among other sensitive components employed within a circuit breaker.
It is a further object of the present invention to improve the reliability and useful life of a circuit breaker.
It is a further object of the present invention to improve the electrical interruption capacity of a typical miniature circuit breaker by increasing the magnitude of current that can pass through the circuit breaker without substantially damaging its sensitive components.
These and other objects of the present invention will be more fully understood from the following description of the invention and by reference to the figures and claims appended hereto.